1. Field of the Invention
Various exemplary embodiments relates to biosignal measuring equipment and, more specifically to equipment that measures a biosignal associated with a vehicle driver using electrodes mounted in a steering wheel of a vehicle.
2. Description of the Related Art
Conventional measuring equipment that uses a pair of left and right electrode units disposed in a ring portion of a steering wheel or spoke portions thereof, detects a potential difference occurring between electrodes when a vehicle driver holds the electrode units with left and right hands, and thereby measures an electrocardiographic complex of the driver is described, for example, in JP-2000-14653A and JP-2002-85360A. It will be understood that the term “electrocardiographic complex” can be considered to refer, for example, to a specific characteristic or series of characteristics of a measured signal or a waveform that indicate specific conditions related to the cardiographic condition of a subject.
However, the conventional measuring equipment is configured to attempt to measure the electrocardiographic complex of the driver merely by detecting a potential difference occurring between the pairs of electrode units disposed on the left and right sides of a steering wheel. Moreover, the left and right electrodes are disposed substantially along the entire periphery of the ring portion or the left and right sides of the spoke portions so that the electrocardiographic complex can be acquired despite a change in the positions on the steering wheel at which the driver holds the steering wheel.
Disadvantages arise however in that in the conventional measuring equipment, electrical noise generated by other electronic equipment mounted in a vehicle and ambient electrical noise existing in the vehicle can be induced into the measuring equipment through the left and right electrode units. Moreover, when an electrocardiographic signal obtained through each electrode unit is weak, noise components cannot be fully removed even by using a filter specifically configured for noise removal resulting in the problem that a signal-to-noise ratio of a finally obtained electrocardiographic complex cannot be increased to such an extent that a potentially abnormal cardiac condition or precursor thereof can be identified.